1. Field of the Invention
This invention relates to enclosures for installation on the seabed to carry communications and/or weapon systems to be deployed from the seabed.
2. Description of the Prior Art
European Patent Specification No. 0110554 discloses an underwater weapon system comprising an elongate outer container which is buried or partially buried in the seabed in an upright position using self-burying means which are at the bottom end of the container and which preferably comprise both pump means for removing sand or silt and rotary material displacing means, e.g. an auger for boring a hole in the seabed or rotary stirring means. The weapon is a self-propelled device with guidance means and is housed within an inner container which is telescopically arranged within the outer container.
U.S. Patent Specification No. 6044745 discloses an enclosure for instalation on the seabed comprising an outer cylindrical container one of the which is more buoyant than the other so that the container lies in a vertical orientation when disposed in the sea and auger devices at the other end of the container for activating sand/silt/shingle on the seabed to create a cavity below the container into which the container can self-bury. The container has a payload compartment within the container for holding weaponry, listening, identification recording and/or communications equipment. The container wall is formed with a plurality of separate passages extending spirally from inlets at the lower end of the container upwardly to outlets at the top of the container through which activated sand/silt/shingle and water generated at the lower end of the container can flow upwardly and freely as the container self-buries in the seabed.
According to a first aspect, the invention provides an enclosure for installation in the seabed, comprising an elongate container for holding a payload, the container having a plurality of passages extending lengthwise of the container and impeller means at one end-of the container to be the lower end of the container on installation for drawing water through at least one of said passages from the other end of the container to form a slurry with the material of the seabed and for discharging slurry formed at said one end of the container through at least one other of said passages to said other end of the container for discharge into the surrounding water.
Preferably the enclosure has inner and outer concentric passageways extending lengthwise thereof and said impeller has a blade or blades extending across the inner and outer passageways, the blade or blades having a first section pitched to draw water down one of the passageways and a second portion pitched to discharge slurry up the other of the passageways.
More specifically the impeller may be rotatable about an axis which is co-axial with the axes of the inner and outer concentric passageways, inner portions of the blade or blades of the impeller being pitched to draw water down the inner passageway and the outer portion of the blade or blades of the impeller being pitched to propel slurry up the outer passageway.
In one particular arrangement the outer passageway may have an annular outlet port partway up the container for the discharge of slurry outwardly of the container.
In any of the above arrangements the payload may include a motor for driving the impeller and a power supply for the motor.
Also in any of the above arrangements the payload may include communication means for receiving/transmitting signals which may be sonar, acoustic or seismic.
The payload may also include a weapon system or systems.
Turning now to further aspects of the invention, worldwide, there are perhaps some several hundred of Mine Hunting Vessels (MHVs) either in existence or under construction. All are designed to a very high standard, costly to build and loaded with even more expensive equipment. They rely on complex and heavy sweep gear, hull mounted sonars, variable depth sonars (Vds), remotely operated vehicles (ROVs) and unmanned underwater vehicles (UUVs) to act as xe2x80x9ceyesxe2x80x9d when trying to find, identify, and neutralise targets. MHVs and other ancillary vehicles therefore constitute the xe2x80x9cpoint of the spear headxe2x80x9d in any amphibious landing or mine clearance operation. Such assets are not easily replaceable.
Currently the only way to find articles such as maritime mines whether moored to or buried in the sea bed is, as indicated, to use various types of sonars.
Some sonars may perhaps even be mounted on ROVs or UUVs and which for each of designation, are hereinafter referred to as xe2x80x9cscoutsxe2x80x9d.
The situation is therefore much as follows. All ships generate signals, even when anchored, dead in the water, or if under way, by various means e.g.:
(a) Seismic Signals
(b) Noise which may be either
(i) Vessel General Signals (xe2x80x9cVGSxe2x80x9d)
(I) Sonar Generated Signals (xe2x80x9cSGSxe2x80x9d)
(c) Pressure changes
(d) Anomalous magnetic signals (MAD)
Sensors already exist which will register-respond, to any one, a combination, or all four of these signals.
Even with the use of xe2x80x9cscoutsxe2x80x9d the useful range at which objects may be detected by sonar is limited, perhaps to say 1,000 to fifteen hundred yards at best, and, without VDS, down to a depth of say 50 fathoms or so. The field of vision or xe2x80x9cswathexe2x80x9d is similarly restricted. Clearance rates are therefore slow, and progress is pedestrian.
In consequence mine clearance is a difficult task even against old fashioned moored and/or contact mines, particularly when coming up against decoys and/or ship count. The situation is not eased if the MHVs are also subject to airborne and other forms of attack, and/or operating under less than ideal sea conditions.
Now, if to all the foregoing hazards is added a self propelled sonar/acoustic signal riding weapon, which is programmed to xe2x80x9cHunt the Huntersxe2x80x9d e.g. the subject of EP-B-0844963 and which being xe2x80x9cpassivexe2x80x9d will detect the xe2x80x9cactivexe2x80x9d searching sonar signal, from whatever source, e.g. MHV or Scout, at twice the range at which the weapon of 0844963 itself can be detected, then the task of mine clearance becomes immeasurably more difficult, and the likely costs to even the most determined aggressor, will hopefully be prohibitive.
Nevertheless some may try, and the following is a further invention will further deter any that do attempt to overcome the arrangement of EP-B-0844963.
Thus according to a further aspect the invention provides an underwater communication device comprising means to detect a signal generated by a vessel in the vicinity of the device and means responsive to receipt of such signal to transmit a decoy sonar signal to the vessel.
It is proposed that in order to deter, confuse intruding vessels, a series of units (referred to herein after as xe2x80x9cLoreleixe2x80x9d) designed to be buried or partially buried/planted in the sea bed, and which will detect and respond to the various signals which will be generated by intruding vessels should be deployed in and around maritime mine fields. They would be particularly effective when deployed in conjunction with the sea bed unit described and illustrated in EP-B-0844963.
Each unit which could be constructed of or coated with non reflective materials, will contain the necessary electronic equipment e.g. receivers, sensors, hydrophones, magnetometers, transducers, transponders, signal generators, aerials, transmitters etc. to enable it not only to accept coded instructions, which might be either seismic or acoustic in origin, but also to ensure that when alerted/activated by the presence of an intruding vessel or decoy, either surface or subsurface, that the signals, particularly such sonar signals emanating from the intruder may:
(a) be received copied, analysed, classified modulated or amplified before being re-transmitted, if, or as required, alternatively,
(b) spurious synthesised signals purporting to be the reflecting echo of different varieties, types, shapes, of mine could be generated and transmitted, as could that of a submarine or running torpedo in order to confuse-blind the searching vessels.
In the same way, such units could also be deployed in the littorals, and/or remote areas, where they could be used as a covert early warning system. They too could be alerted by say:
(a) Seismic signals, followed by
(b) Acoustic and/or magnetic anomaly signals
(c) Pressure generated signals. These signals cannot currently, be synthesised, and would therefore be extremely useful in confirming the class of vessel, submarines for instance have a particularly distinctive pressure pattern signature, and with the units tuned accordingly, would be comparatively easy to plot!
Having intercepted the various signals emanating from vessels and confirming say, that it is a submarine, the unit could release a buoyant radio beacon which would:
(a) transmit a uniquely coded radio signal, thereby confirming its authenticity, before it would
(b) self destruct and release a calcium carbide float, and/or fluorescent coagulate dye which would spread across the surface of the sea, and which would therefore, be visible to the xe2x80x9csatellitexe2x80x9d tracking systems. Different coloured dyes might be used:
(i) to identify different types of vessels, and/or
(I) to indicate time of release.
In this way the course of a submarine could be charted from the time it leaves its base. The use of xe2x80x9cdecoy dyesxe2x80x9d by vessels would be precluded by the need for the dye release to match with the xe2x80x9cunique coded identification signalxe2x80x9d.
Battery life will be important in such units, therefore the arrangement could be programmed to listen for instructions at pre-determined times, rather than maintain at a constant listening watch. Instructions would be coded and might for instance initiate one of the following pre-programmed modes, e.g.:
(a) remain dormant unit . . . or
(b) await further instructions which will be issued at pre-determined intervals or
(c) become active, for a period, or permanently, or
(d) set to anti handling mode, or
(e) self destruct if breaking from its mooring, or if so instructed.